Propylene polymerization with hf-bf



B. L. EVERING ETAL PROPYLENE POLYIIERIZATION WITH HFBF3 Nov. 71950 2 Sheets-Sheet 1 Filed July 3, 1948 @Sit INVENTORS: Bernard L. Everng Edwin F peers TORY Nov. 7, 1950 B. L Evt-:RING Erm.

PROPYLENE POLYMERIZATION WITH PIF-EP3 Filed .my s, 1948 2 'Sheets-Sheet 2 QH E: N.

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.SS E Ek *QBOQ moo" Lnxkvlwn btobotou INVENTORS:

.Ws Wn M 5% L F d WW r n @www Patented Nov. 7, 1950 raorYLENE roLYMEmzATIoN wrrn HF-BF:

Bernard L. Evering and Edwin F. Peters, Chicago,

lll., assignors to Standard Oil Company, Chicago, lll., a corporation of Indiana Application July 3, 1948, Serial No. 37,038

This invention relates to propylene polymerization with HF-BFa catalysts and it pertains more particularly to improved methods and means for directing said polymerization toward the formation of tetramers and pentamers, i. e. olefin polymers containing 12 and 15 carbon atoms per molecule respectively.

It is well known that propylene can be polymerized with a wide variety of catalysts such as aluminum chloride, phosphoric acid, boron fluoride and hydrogen fluoride-boron fluoride mixtures. These known processes, however, have been directed toward the production of gasolineboiling range polymers or more or less viscous oils of high molecular weight. An object of this invention is to provide a method and means for directing HF-BFa polymerization of propylene toward the production of C12 and C15 polymers which are suitable for the manufacture of detergents, such polymers being commonly referred to as "detergent polymers because of their intended use in the preparation of detergents. Small amounts of such polymers are formed in various known processes but such amounts are usually too small to warrant the use of such processes for detergent polymer manufacture and furthermore such processes frequently are accompanied by side reactions such as hydrogen transfer which renders the polymers unsuitable for detergent manufacture. For example. when propylene is polymerized with AlCla only about 6% of the total product is in detergent polymer range and the proportion which is within the desired range is more saturated than desirable for use in detergent manufacture. An object of the invention is to provide a process which will produce a polymer containing at least about 40% of unsaturated hydrocarbons in the C12-Cia range.

Hofmann and Otto (U. S. 1,885,060) showed that propylene could be polymerized with BF.; to yield more or less viscous oils and numerous investigators since that time have explored the field of olefin polymerization by means of such catalysts. INone of these investigators, however, have shown how the polymerization reaction can be controlled to give C12-Cin polymers as the predominant product. An object of this invention is to provide an improved method and means for effecting HF-BFa polymerization of propylene whereby the amount of detergent polymer exceeds not only the amount of gasoline-boiling range polymers but also exceeds the amount of higher boiling viscous polymers and wherein the detergent polymer thus formed is not appreciably saturated by hydrogen transfer during the catalyst Claims. (Cl. 26o-683.15)

merization zone.

polymerization reaction. A further object is to avoid the necessity of recycling Ce or C9 polymers as is usually necessary when phosphoric acid is employed as a polymerization catalyst. Other objects will be apparent as the detailed description of the invention proceeds.

We have discovered that the objects of our invention can be accomplished by effecting the polymerization of propylene in the presence of a diluent such as propane under a pressure sufficient to maintain liquid phase polymerization conditions, e. g. of the order of about 300 to 600 p. s. i. g. and at ordinary temperatures within the range of about 40 to 120 F. provided that a single homogeneous liquid phase is maintained in the poly- The reaction pressure should be sufiicient to maintain both the HF component oi' the catalyst and the reactant and diluent in liquid phase condition and the amount of HF employed should be sufficiently small so that it is completely soluble in the propylene-plus diluent (and reaction product). The solubility of HF in propaneunder a pressure of' about 400 p. s. i. and a temperature of about F. is about 2.4 weight percent. We have discovered when this amount oi' HF is exceeded, the polymerization reaction is directed toward production of high molecular weight polymers but that on the contrary when the amount of HF is appreciably below the solubility limit, a remarkably large amount of detergent polymer is produced, the amount being greater than either the amount of gasoline-boiling range polymer or the amount of high molecular weight polymer. We prefer to eiiect the polymerization continuously and to regulate or control the amount of introduced HF to insure a homogeneous HF-hydrocarbon liquid phase in the conversion zone.

The most active catalyst is one containing HF and BFsin approximately equal molar proportions. Although in many processes catalyst composition has a marked effect on product distribution, we have found that in our process the mol percent of HF and BFa in the catalyst may be varied throughout an enormously wide range without appreciably affecting the nature of the product formed provided that the HF component is well below the solubility limit in the hydrocarbon components. The time required for effecting polymerization is preferably of the order of about 5 to 15 minutes although shorter or longer times may be employed without materially affecting product distribution. The diluent is preferably propane although other inert hydrocarbon diluents may be employed and the amount of diluent is preferably in the range of about 1 :5 to 5: 1. By dissolving the HF component of the catalyst in the hydrocarbon diluent, such as propane, and introducing it into the polymerization system as a solution, we can insure the necessary homogeneous liouid phase condition and the production of at least about 40% to 50% detergent polymer in the total conversion product, the extent of conversion usually ranging from about 50% to 100%.

In most olen polymerization processes it is an accepted rule that lowering polymerization temperature results in increasing the molecular Weight of the polymer product. In our process we have found that increasing the polymerization temperature to as high as 180 F. has an effect which is directly opposite to the expected eiect. At room temperature we obtain a detergent polymer yield of about 40% to` 50% or more and a high molecular weight polymer (C24-H yield of only about '10 to 20% while at 180 F. our detergent polymer yield is only about 18% and the high molecular weight polymer yield is 50%.

The invention will be more clearly understood from the following detailed description and the cited examples read in coniunction with the accomnanving drawings which form a part of the specification and in which Firfure 1 is a schematic flow sheet diagrammaticallv illustrating a continuous polymerization unit for carrying out our process, and

Figure 2 is a graph illustrating the remarkable effect of liouid phase PIF-hydrocarbon homogenietv on product distribution.

Referring rst to Fleure 1. propylene is introduced through lines I and II to rnixer I2, which is surrounded bv cooling jacket I2a, and thence through reactor tube I3 to the lower part of reaction chamber I4. the pronylene being admixed in mixer I2 with BFa introduced through line I5 and HF (preferably in the form of a propane-HF solution) introduced through line I6. Preferably make-up and recovered HF is initially introduced by line I1 to vessel I8 in amounts sufcient to maintain a substantial column of liquid HF in vessel I9. Propane or other inert hydrocarbon diluent is introduced by line and at least a portion of the introduced propane passes in liouid phase through line 2I upwardly through the column of HF and thence through line 22 to line I6. The amount of HF introduced can be controlled by by-passing a part of the introduced diluent through line 23.

In this particular example about 2 volumes 0i g propane are. employed ner 3 volumes of pronylene in the total charge; while it is preferred to introduce. at least a part of the propane through lines 20, 2| and column I9 in order to solve the metering and control problem, the propane may be introduced in admixture with propylene through line I0 and the malte-un and recovered HF may be introduced in regulated amounts directly through line I6. The totalcatalyst in this particular example may contain about 40 to 50 mol percent HF and 60 to 50 mol percent BFa. Such total catalyst may be employed in amounts of about 3 to 4 mol percent based on propylene charged or about 2 to 3% based on total hydrocarbon charged, the total weight percent of HF in the charge thus being about 0.5%. In order to remove impurities from the propane and propylene such hydrocarbons may be given an initial caustic wash in which case they should be water washed and thoroughly dried with calcium chloride or other known drying agents before being introduced into the system.

The homogeneous propane-proylene-HF mixture is intimately mixed with the BF: in mixer I2 which may be of any known type and the intimate mixture is then rapidly introduced through reaction tube I3 to the base oi' reaction chamber I4 where the introduced reactants and catalyst may be distributed by baule Ia or other known distributing means. The reaction chamber should be provided with cooling surfaces which are diagrammatically illustrated as coils I6a. The cooling may be effected by circulating the cooling water around reaction tubes which are secured at each end to headers and other known types of heatexchange may be employed. The temperature of the reactor should preferably be of the order of about 70 to 110 F. although reactor eiiiuent may reach temperatures as high as to 140 F. The contact time in the reaction tube or tubes is preferably about 5 to 50 seconds, e. g. about 30 seconds and in the total reactor may be as great as about 5 to 15 minutes. The reaction pressure should be suilicient to maintain both the HF and the hydrocarbon charge in liquid phase condition such a pressure being in this case of the order of about 400 p. s. i. s'.

Reactor eftluent passes by line 24 to settler 25 wherein any small amount of complex which may vbe formed can settle out and be withdrawn to line 26. Similarly, any complex that might otherwise tend to accumulate in reactor I4 is withdrawn by line 21; it is highly desirable that any such complex be removed as rapidly as it accumulates because such complex tends to act as a separate liquid phase which, in the presence of HF, tends to direct conversion toward high molecular weight polymers instead of the C12-Cu polymers. The withdrawn complex may be treated in known manners for recovery of HF and BF3 and/or it may be hydrolized for production of drying oils or other types of byproducts. It should be emphasized however that under the preferred conditions of operation less than 1% of the charge is converted into complex.

If BF; or other gas tends to accumulate in the upper part of the reactor I4 or settler 25, such gas may be withdrawn through lines 28 and 29. The reactor should be carefully designed to attain intimate mixing and uniform distribution of the BFa and it is important that BF: (or other gas) should not accumulate in the system.

The product stream from settler 25 is withdrawn through line 39 and heat exchanger 3I wherein it is heated to a temperature of about 250 F. before it is introduced into depropanizer tower 32. Any gases vented through lines 28 and 29 may likewise be introduced into tower 32 through line 33. Tower 32 may be operated at a pressure of about 260 p. s. i. g. with a top temperature of about F. and a bottom tem perature of about 480 F. the latter being obtained by use of suitable reboiler or heating means 34. The overhead products are cooled in condenser 35 and introduced into separator 36 wherein both HF and gas are removed from hydrocarbon liquid. The hydrocarbon liquid condensate is removed from the separator by pump 31 a part of the condensate being returned by line 38 to serve as reflux in tower 32 while the remainder is introduced by line 39 to stripping tower 40 provided with a heater 4I at its base for maintaining a bottom temperature at about 140 F. Propane-HF-azeotrope from the top of the stripper is returned from line 42 to the stream entering cooler 35 and settler 38. The HF-free propane is removed from the base of the stripper through line 43 and a part of this propane, if it contains no substantial amounts of propylene, may be recycled by line 44 to serve as diluent thus eliminating the necessity of introducing propane via line 20. Since only a small amount of BFb is present in the stream in line 39, the recycle stream for line 44 may come directly from line 39 and thus decrease the load on stripr 40. p@The BFa containing gases from separator 36 are introduced by line 45 to the lower part of tower 46 and settled HF is introduced from the bottom of separator 36 by line 41 to an intermediate point in the packed tower. Xylene at about 130 F. is introduced by line 48 at the upper part of packing tower 46 for combining with the BFa in the form of a complex, thus eliminating Bl from residual gases which are vented through line 49 which preferably discharges into a caustic scrubber. Xylene-BF; complex and HF are withdrawn from tower 46 by line 58 and introduced into bailled tower which may operate at about 35 p. s. i. g. and at a temperature of about 300 F. which is maintained by steam coil 52. HF and released BFs pass overhead through cooler 53 to condensate receiver-separator 54. Xylene leaves the base of baflle tower 5| and after being cooled in cooler 55 to a temperature of about 130 F. it is reintroduced by pump 56 at the upper part of tower 46.

The BFa which is separated in receiver-separator 54 is returned by line 51 and compressor 58 to the reactor. Condensate from receiver-separator 54 is withdrawn by pump 59 and a part of it is returned by line 60 to serve as reflux in baille tower 5| while another part is introduced into tower 6| which is operated at about 70 p. s. i. g. with a bottom temperature of about 230 F. which is maintained by heater 62. Substantially anhydrous HF is taken overhead through condenser 63 to receiver 64. A part of the condensate removed by pump 65 is returned by line 66 as reflux while the remainder is Withdrawn through line 11 for recycle to the system, preferably to vessel I8.

The depropanized polymer from the base of depropanizer 32 passes by line 18 through heat exchanger 3| and thence through one or more bauxite treaters 19 and line 88 to gasoline fractionating tower 8| which may operate at about 20 p. s. i. g. with a bottom temperature of about 500 F. maintained by heater 82. The overhead gasoline fraction is condensed in cooler 83 and collected in receiver 84 from which a part of it is returned by pump 85 and line 86 to serve as reflux while the net gasoline fraction is withdrawn through line 81. A system designed to charge about 1500 barrels per day of propaneprooylene charging stock as hereinabove described may yield about 150 to 200 barrels per day of gasoline-boiling range polymers.

The polymer fractions higher boiling than gasoline are introduced by line 88 to fractionatlng tower 89 which is preferably operated at about 350 mm. mercury absolute pressure with a top temperature of about 365 F. and a bottom temperature of about 550 F. maintained by heater 98. Cra and heavier polymers lare withdrawn from the base of tower 89 through line 8|. The overhead from tower 89 is condensed in cooler 92 and collected in receiver 93. A part of this condensate is returned by pump 94 and line 85 for reflux in tower 89 and the net production of C12-C15 polymer is withdrawn through line 88. Y In this particular c ase upwards of 300 barrels per day of Cra-C15 polymer can thus be produced which polymer has not been saturated by hydrogen transfer. The polymer thus producedis particularly suitable for the manufacture of detergents. 'The heavier viscous polymer withdrawn through line 9| may amount to less than 150 barrels per stream day.

'I'he C12-C15 polymer fractionation differs from propylene polymer produced by AlCh polymerization not only because it is less saturated on account of hydrogen transfer but also because it consists essentially of monomer multiples. Le. C12 and C15 hydrocarbons with very little C13 and Cnl hydrocarbon material. In phosphoric acid polymerization or propylene the desired amounts of C15 polymer are formed by recycling Ca and C9 polymers but in our process such recycling. is unnecessary and is in fact of little or no value.

While a commercial scale example of our process has been described it should .be understood that the invention is not limited to the specific proportions, operating conditions, etc, therein set forth. For a more complete understanding of the invention reference willbe made to typical data obtained in a. small scale continuous reactor with various amounts of dlluent. catalyst compositions, catalyst concentrations, contact times. etc. The small scale reactors were 28 inches long and inch, l inch and 11/2 inches in internal diameter providing total reactor volumes of 6l. 275 and 680 ml., most of the work having been done in the largest reactor. A lrinch tubular reaction pipe approximately 25 inches long (corresponding to element I3 in reactor I4) introduced the reacting mixtures at the base of the reactor and the reaction took place with the reactor surounded by a water packet for maintaining substantially consta-nt polymerization temperature. Diiculty was encountered in metering HF directly into the reaction mixtureand best results were obtained when the HF was introduced as a propane solution. The reactor effluent was introduced into a polymer receiver which discharged gasiform materials to a soda lime tube for acid vapor recovery and a solid carbon dioxide condenser to recover` the propane diluent and unconverted propylene. Representative reaction conditions and results are illustrated in the following table.

Run A B C D E F G H l J Hydrocarbons:

Propylene grams 302 l, 035 l, 635 705 845 597 636 537 992 885 lropane grams 101 270 756 177 2, 295 150 160 144 2, 670 2. 340 :ita yst:

BFz, grams 2l. 8 66.0 45. 5 14. 3 52. 4 90. 5 107. 5 Z3. 8 2l. 8 HFJ. grams Trace 1.4 4. 8 3. 4 38. 6 15.4 20. 6 3l. 0 17. 4 16. 0 Weight pc cent HF Fn(based on chargel 23. 7 1.8 2. 9 5. 2 l. 7 8. 3 l2. 5 16.8 l.l L2 Mol. per nt- HF ln FIF-BF; .l 18 20 20 90 50 50 50 7l 7l Weight per cent HF as chargc l 0. ll 0. 20 0. 39 l. 23 2. 06 8. .7L 4. 66 0. 47 0. 50 Experimental Cond.:

Y Temp. F 110 ll0 110 110 li0 ll0 ll0 ll0 IM 45 Pres., p. s. i. g 400 440 440 440 440 440 440 440 000 400 Contact time, mln. 25 l5 l5 l5 7. 5 l5 l5 l5 il l1 l `thus converted into the undesirable viscous oils of high molecular Weight. Solution kof HFl in `introduced propane is a sure safeguard against Run A B o D n r G H I J Weight per cent conversion 92 70 69 39 79 85 92 85 73 49 PolT-effsll 7 1s 2o 14 2e e 1 e 1o 1o ,-c- 51 4s 52 54 4s as 1o s 1s 4a een- 23 11 1a is 1e zi 12 13 22 zo 024+ 19 22 12 14 1o 33 71 7.: 6o 21 Wyiftgl 1 1 1 1 1 a a 15 1 1 The data set 'forth in the above table is typical may be maintained at all times by other operof a vast amount of data which has been acquired ating procedures-for example, a portion of the from which many surprising results may be propylene charging stock may rst be reacted stated. Of extreme importance is the weight perl5 with HF to form a propylene fluoride and in the cent HF charged to the reactor. Under the conmixer or conversion zone the propylene fluoride ditions employed, i. e.' at a temperature of 110 may liberate HF so that at no time is the HF in F. and a pressurev 'of S400 p. s. i., the solubility a separate liquid phase. While substances which of HF in .propane is about 2.4 Weight percent. afford HF may thus be used in place of HF it- When substantially less than this amount of HF 20 self, such substances cannot be considered as was employed, at about 110'V F., about 40 to 60% the equivalent of HF and for best results and 0f 012.015 polymer was obtained regardmss of smoothest operation We prefer to introduce the the propane-propyle'ne ratio, the mol percent HF aS Such. H111 in the EF1- B115 andy they weight percent The mol percent of the HF in the HF-BF is of HF-BF-a. basedV on charge (note Runs A not of great importance. Even a trace of HF is to -E inc1us1ve) When the amount of HF emsuflicient to accomplish the desired results (note ployed was sufficient to exceed its solubility in Ren A) The mOSt active Catalyst iS One conthe hydrocarbon charge, vthereby resulting in taming ebOUt equal Darts 0f HF and BFa on a the formation ofa heterogeneous liquid phase in o m01 basis. .From an operating standpoint, it the polymerization zone, the amount of C12-C15 3o may be deslrable t0 employ about 40 to 50 m01 `polymer suddenly dropped to a remarkable ex- Percent 0f HF 1X1 the HF-BFs mixture because .tent and the chief productv of the reaction was HF can be recovered more easily and Completely viscous high molecular 'weight polymers (note and because aDDIOXlmately this amount of HF Runs'G and H) vevwhen the Weight percent in the catalyst composition is required for maxi- HF was 2.06 (Run fp) there apparently was a mum propylene cleanup. However, it should be phase separation in a part or parts of the reactor feaslble t0 Operate fljom less than Y10% t0 11pbecause the C12-C15 polymer yield dropped to Wards 0f 90% 0f HF 1n the Catalyst Composition 38% and there was a.' -marked increase in the and throllghput this Composition range the viscous polymer yieldl ,product distribution is remarkably constant.

Another striking feature is the fact that when; 40 j '.Ihe effect of temperature 1s also surprsing in homogeneous phase ,conditions are employed this process. As temperatures are increased (i. e. when the weight percent HF was well below from about 40 t0 180 F- the yield 0f C12-C15V 01e- 2'4 percent) very Complex was fins markedlyfalls O the of viscous formed, the amount vin all cases being about 1% polymers 0f hlgh molewla-l Weight markedly inor less; however, after the separate liquid HF creaes" the Weld UfC-Cg Olens Teaming a phase is formed (due to the use of HF in amounts 45. maxlmmffmd the' yieldtof 0184321 olens reachin excess of 2.4 weight percent of charge) there mg a mmlmum at about F: (with Catalyst is a sharp increase in complex formation as concentration at111 Weight Percent. Catalyst shown by Runs G and H composition of '711 mol percent HF and contact The striking effect of HF concentration on time 11 minutes). Runs I and J when compared product polymer composition is shown in Figure 50 With Runs D and E fOr example illustrate the 2 which graphicauyinnustrates the fact that effect 0f temperature and indicate thet'the temproduct distribution may graduauy change with perature should be markedly lower than F. the Weight percent HF in feed in the region beand preferably should be in the range of about 45 low about 2 Weight percent and also in the region t0 110 F- I above about 3 weight percent but that there is a 55 In 0111' DIOCeSS the diluentv Serves an impordiierence in the type or kind of polymerization tant function in addition to that which suchv which is eiected in these two regions. Where diluents performed in prior polymerization procthe amount of HF is such that a homogeneous esses. The diluent dissolves the I-lIF and insures liquid phase is assured the products are pre-v the maintenance ofa homogeneous liquid phase dominantly C12-C15 polymers. When the amount 60 during the continuous pelymeriZe-tien reaetiOn. of HF is suiicient to produce a heterogeneous Preferably the diluent also serves as a vehicle `phase the products are almost entirely viscous for introducing the HF in desired amountsand high molecular weight polymers. when the HF is so introduced it cannot possibly The phenomena illustrated in Figurev 2 and form a separate liquid phase in the polymerizain the tabulated data explains the difficulties o5 tion zone. encountered in attempts to produce large yields We claim: e 0f C12-C15 DOlymel by metering HF direetly into 1. The method of producing C12-C15 polymers the reactor. In such operations, itis diflicult to by the polymerization of Y propylene with an prevent hetelOgeneOUS liquidrphaSeS at leaSt in HF-BFa catalyst which method comprises conthe mixing Zone and a part 0f the Olens are 70 tacting said propylene and said catalyst at a temperature in the range of about 40 to 140 F. under a pressure sufficient to maintain both the propylene and HF in liquid phase condition and employing a sufficiently large amount of an inert diluent in which HF is soluble to an appreciable extent and a sumciently small amount oi HF in the catalyst composition so that the HF will be completely dissolved in the diluent-propylene mixture during the polymerization.

2. The method of producing large yields of tetramer and pentamer in the polymerization of propylene with an HF-BFa catalyst which method comprises effecting said polymerization in the presence of an inert diluent in which HF is soluble to a certain extent, effecting the polymerization at a temperature higher than about 40 F. but lower than about 140 F. under a pressure sufficient to maintain the propylene and HF in liquid phase and limiting the amount of HF to a value substantially below its solubility under the polymerization conditions whereby the polymerization is .effected with all liquid compo'- nents in homogeneous phase condition.

3. The method of polymerizing propylene with an HF-BFa catalyst to obtain low molecular weight polymer rather than viscous high molecular weight oils as the preponderant product, which method comprises dissolving the HF component of the catalyst in an inert diluent, intimately admixing the resulting solution with propylene and. the BFa component of the catalyst and contacting said mixture in the polymerization zone maintained at a temperature in the range of about 40 to 140 F. and a pressure in the range of about 300 to 500 pounds per square inch 4. In the method of eecting a hydrocarbon conversion with an HF-BFa catalyst under conditions wherein both hydrocarbon and HIF are in liquid phase, the improvement which comprises dissolving the HF component of the HF-BFa in an inert diluent at a temperature which is not substantially higher than conversion temperature and contacting the hydrocarbon and BFa component with said solution under homogeneous liquid phase conversion conditions.

5. The method of effecting hydrocarbon conversion with an HF-BF: catalyst which method comprises passing an inert diluent having a solvent power for HF through a column of HF to produce a diluent-HF solution, intimately admixing said solution with BF; and the hydrocarbon to be converted and effecting conversion under sumcient pressure to maintain both the hydrocarbon diluent and the HF in homogeneous liquid phase condition.

6. The method of polymerizing propylene with an HF-BF3 catalyst which comprises dissolving the HF catalyst component in propane, admixing the resulting solution with propylene and the BF; component of the catalyst, passing said mixture through a polymerization zone at a temperature in the range of about 40 to 140 F. at a presization zone.

8. A continuous processior producing olenic hydrocarbons containing about 12 to l5 carbon atoms per molecule which process comprises intimately mixing propylene, propane, HF and BFa and passing said mixture through a polymerization zone, maintaining said zone at a temperature in the range of about 40 to about 140 F. and at a pressure in the range of about 300 to about 500 p. s. i. sufficient to maintain both the propylene and HF in liquid phase, employing a suiliciently large amount of propane and a suiliciently small amount of HF so that said liquidphase will be homogeneous, discharging polymerization zone effluent to a settling zone, removing complex material from said eiliuent in said settling zone, passing the remaining eilluent to a. depropanizer zone, separating propane and lower boiling components from higher boiling components in the depropanizing zone, separating the overhead from the propanizing zone into a propane fraction, a gas fraction, a BFa fraction and an HF fraction, returning the BF: and HF' fractions to the polymerization zone and fractionating the depropanized components into a gasoline boiling range fraction, a fraction consisting of C12-C15 hydrocarbons and at least one heavy polymer fraction.

9. The method of claim 8 which includes the step of purging gases from the reaction mixture before said mixture is introduced into the depropanizing zone and introducing said gases into said depropanizing zone.

10. The method of claim 8 which includes the step of dissolving HF in propane prior to said mixing step.

BERNARD L. EVERING. EDV/LN F. PETERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,318,719 Schneider May 11, 1943 2,401,933 Hersberger June 11, 1946 2,416,106 Linn et al. Feb. 18, 1947 2,431,454 Berk Nov. 25, 1947 2,436,929 Linn Mar. 2, 1948 

1. THE METHOD OF PRODUCING C12-C15 POLYMERS BY THE POLYMERIZATION OF PROPYLENE WITH AN HF-BF3 CATALYST WHICH METHOD COMPRISES CONTACTING SAID PROPYLENE AND SAID CATALYST AT A TEMPERATURE IN THE RANGE OF ABOUT 40 TO 140*F. UNDER A PRESSURE SUFFICIENT TO MAINTAIN BOTH THE PROPYLENE AND HF IN LIQUID PHASE CONDITION AND EMPLOYING A SUFFICIENTLY LARGE AMOUNT OF AN INERT DILUENT IN WHICH HF IS SOLUBLE TO AN APPRECIABLE EXTENT AND A SUFFICIENTLY SMALL AMOUNT OF HF IN THE CATALYST COMPOSITION SO THAT THE HF WILL BE COMPLETELY DISSOLVED IN THE DILUENT-PROPYLENE MIXTURE DURING THE POLYMERIZATION. 